Photonic System-in-Package technologies using thin glass substrates

The novel packaging approach glassPack is introduced as a system-in-package (SiP) technology. Wiring length can be reduced and integration density can be increased by stacking different assembled substrate layers and interconnecting them resulting in 3D-SiP. Glass is an excellent substrate material because of matched coefficient of thermal expansion (CTE) to silicon, high thermal load, dielectric constant and high optical transparency over a wide wavelength range. Commercially available thin glass foils can be used as substrate materials for electronic and optoelectronic modules. The goal of our ongoing development is to make glass based packaging competitive with polymer (e.g. chip-in-polymer) or silicon based packaging (e.g. silicon-through-via, stacked dies by wire bonding). Our work is focused on conductor trace and through-via realization as well as optical lightwave circuit integration using glass as a substrate. For through-glass-vias, holes were drilled in glass wafers by different laser technologies and evaluated. Also, optical integration of waveguides and mirrors in glass substrates were investigated. This paper presents basic design rules and a selection of technologies for glass based SiP as well as a process flow for glass interposer applications.